Diphasic fluid distributing device

ABSTRACT

A device for distributing a diphasic fluid consisting of a gas and a liquid, placed in an enclosed space elongated in a roughly vertical direction, consisting of a roughly horizontal plate dividing the said enclosed space into an upstream part and a downstream part, the said upstream part incorporating a separator, in which the said plate contains a number of pipes, one portion of which opens into the upstream part and the other portion of which opens into the downstream part, and also possibly containing a number of channels providing communication between the upstream and downstream parts. The distribution plate contains two partitions, perforated with channels, roughly horizontal and close to each other, the said channels in the said partitions being distributed uniformly over each partition.

United States Patent [191 Cappiello et al.

[451 Aug. 28, 1973 DlPI-IASIC FLUID DISTRIBUTING DEVICE [75 Inventors: Pierre Cappielio; Joseph Gauberthier, both of Paris, France {22] Filed: July 28, 1970 [21] Appl. No.: 58,776

[73] Assignes:

[30] Foreign Application Priority Data July 9, 1970 France 7023898 [52] US. Cl 55/269, 55/385, 55/462, 62/525, 165/163, 261/110, 261/153 {51] Int. Cl 801d 53/00 {58] Field of Search 55/220, 224, 226, 55/229, 239, 251, 267-269, 385; 62/525,

2,966,038 12/1960 Rice et a1 62/42 X 2,966,958 1/1961 Sexton 55/224 3,546,851 12/1970 Hardison et a1. 55/257 X 3,482,625 12/1969 Bray 165/163 X 3,397,513 8/1968 Ephraim et a1. 55/233 FOREIGN PATENTS OR APPLICATIONS 380,804 12/1907 France.... 55/268 1,351,575 12/1962 France 55/268 Primary Examiner-Frank W. Lutter Assistant Examiner-Vincent Gifford Attomey-Young & Thompson [57] ABSTRACT A device for distributing a diphasic fluid consisting of a gas and a liquid, placed in an enclosed space elongated in a roughly vertical direction, consisting of a roughly horizontal plate dividing the said enclosed space into an upstream part and a downstream part, the said upstream part incorporating a separator, in which the said plate contains a number of pipes, one portion of which opens into the upstream part and the other portion of which opens into the downstream part, and also possibly containing a number of channels providing communication between the upstream and downstream parts. The distribution plate contains two partitions, perforated with channels, roughly horizontal and close to each other, the said channels in the said partitions being distributed uniformly over each partition.

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DIPHASIC FLUID DISTRIBUTING DEVICE The present invention relates to a heat exchange device using a homogeneously distributed diphasic fluid.

In the field of gas liquefaction, heat often has to be exchanged between a diphasic fluid and one or more other fluids. For instance, if natural gas is liquefied by using the incorporated cascade" cycle technique, the natural gas is gradually cooled at high pressure by passing through several successive exchangers, in which the heat exchange is performed by counter-flow with a liquid-gas cold-generating mixture at low pressure and in the course of vaporization.

Wound exchangers are often used for such heat exchanges. In such cases the diphasic fluid is circulated in the exchanger in a vertical direction, around the wound pipes. It can be circulated upwards or downwards.

The wound exchanger or exchangers in which the diphasic fluid is circulated generally forms part of an installation producing the diphasic fluid in a very heterogeneous form. In some cases, for instance, the diphasic fluid supply is in the form of quantities of liquid separated by pockets of gas. The diphasic fluid therefore cannot be injected in this form into the exchanger, but first has to be tranquillized in a separator situated in front of the wound exchanger.

In the case of upward circulation of the diphasic fluid, the liquid from the separator is distributed over a perforated plate placed below the wound pipes, and the gas from the separator is simultaneously injected below the plate, avoiding any filtration of the liquid through the plate.

In the case of downward cirulation of the diphasic fluid, the liquid from the separator is distributed over a perforated plate placed in the wound exchanger above the wound pipes, and the gas from the separator is injected through the liquid held back by the perforated plate.

For small-diameter wound exchangers, fairly homogeneous distribution of the diphasic fluid can thus be achieved. For large-diameter exchangers, however, (the shell of which can be 4 to 5 meters in diameter, for example), it has been found in practice that these methods of distribution become defective, and lead to heterogeneous distribution of liquid and gas. It has been noted in particular that this is due mainly to the fact that the liquid is never distributed uniformly over the perforated plate placed above or below the wound pipes of the exchanger.

This heterogeneous distribution of the diphasic fluid affects the proper functioning of a wound exchanger. If one assumes, for example, that the gas phase is concentrated in one part of the exchanger and the liquid phase in another part, serious corresponding variations in the exchange coefficient will occur from one part to another, as well as a thermal unbalance. If the diphasic fluid circulating around the exchanger pipes is a gas vapor mixture of pure components in the course of condensation, condensed fractions with different temperatures and compositions will occur at the exchanger outlet.

In addition, when one is calculating and establishing the dimensions of the wound exchangers according to the present invention, exchange diagrams, exchange coefficients and pressure losses are assessed on the basis of homogeneous distributed diphasic fluid. It is therefore essential to obtain such homogeneity during the operation of the wound exchanger, so as to ensure the performances expected when designing the exchanger.

The aim of the present invention is to remedy all these drawbacks.

The present invention relates to a process for distributing a diphasic fluid consisting of a gas and a liquid, in which at least part of the liquid and at least part of the gas, both coming from a separator placed in front of a distribution plate which is on a first roughly horizontal plane, pass through the said plate in the form of a number of gas jets and liquid jets moving in the same direction, uniformly distributed in the said first horizontal plane.

The present invention concerns a device for distributing a diphasic fluid consisting of a gas and a liquid, placed in an enclosed space elongated in a roughly vertical direction, consisting of a roughly horizontal plate dividing the said enclosed space into an upstream part and a downstream part, the said upstream part incorporating a separator. According to the present invention, the said plate contains a number of pipes, one portion of which opens into the upstream part and the other portion of which opens into the downstream part, and it may also contain a number of channels providing communication between the upstream and downstream parts.

The present invention also concerns a wound exchanger consisting of a shell elongated in a roughly vertical direction, one or more layers of pipes inside the said shell, and enabling heat to be exchanged between a diphasic fluid circulating inside the layer or layers of pipes and one or more other fluids circulating in the layer or layers of pipes, the said shell containing a roughly horizontal plate dividing the exchanger into an upstream part incorporating a separator and a downstream part incorporating the layer or layers of wound pipes according to the present invention, the said distribution plate contains a number of pipes, one portion of which leads into the upstream part and the other portion of which leads into the downstream part, and it also may contain a number of channels providing communication between the upstream and downstream parts.

The invention therefore basically enables the liquid phase of the diphasic fluid to be distributed uniformly and homogeneously over a distribution plate situated in front of or behind the nest of tubes, depending on the direction taken by the diphasic fluid in circulating around the pipes of a vertical wound exchanger. The invention correspondingly enables obtaining a uniformly distributed diphasic fluid when the gas phase of the said fluid is combined with the said liquid phase upstream of the nest of tubes. This result is especially important in the case of wound exchangers, since it has been observed experimentally that this homogeneity, obtained upstream of the nest of tubes, is maintained in time and space when the diphasic fluid passes around the wound pipes.

The invention also provides a number of additional advantages. The distribution devices according to the invention provide very stable operation. In the case of upward circulation, this is due first to the selfregulating capacity of the device, enabling slight, temporary variations in the liquid level in the separator to be compensated for, and second to the considerable inertia of the device, which ensures that disturbances of the surface of the liquid in the separator have no effect on the distribution of the liquid over the distribution plate. The device is also very flexible in operation, allowing major variations in the time of flow of the diphasic fluid to be compensated for (such as operation of the installation at 50 percent of its nominal capacity). In the case of a device with upward circulation, for instance, when the installation is operating at 70 percent nominal capacity, the liquid never rises in the separator to such a height that the velocity of the gas becomes great enough to draw the liquid along directly.

Devices according to the present invention operate with small pressure losses. In the case of a device with upward circulation, the liquid in the separator is extracted and put into circulation with little loss of pressure, and the diphasic fluid can be brought downstream of the distribution plate with a smaller pressure loss than that involved in the passage of the liquid on its own through the pipes.

Several forms of embodiment of the present invention are described below, in the case of upward circulation and in the case of downward circulation of the diphasic fluid, with reference to the accompanying drawings.

FIG. 1 shows a vertical cross-section of the lower part of a wound exchanger incorporating a distribution device to circulate a homogeneous diphasic fluid in an upward direction in the exchanger.

FIG. 2 shows a vertical cross-section of the upper part of this same wound exchanger.

FIG. 3 shows a separate vertical cross-section of part of the device illustrated in FIG. 1, and more particularly of the unit formed by two upper crowns, one lower stop crown and two upward pipes.

FIG. 4 shows a perspective view of part of the distribution device illustrated in FIG. 1, and more particularly of the unit formed by one upper crown, two lower stop crowns, an upward pipe and a pipe forming part of the exchanger winding.

FIGS. 5a 5d show various upward pipes according to the invention.

FIG. 6 shows a vertical cross-section of part of another upward distribution device according to the invention.

FIG. 7 shows a partial view of another upward distribution device according to the invention.

FIG. 8 shows several operating curves for an upward distribution device, where the liquid flow through an upward pipe is expressed in relation to the height of slit free for given pressure losses.

FIG. 9 shows other operating curves for an upward distribution device, where the gas flows through the upward pipes and distribution plate respectively are expressed in relation to the pressure loss, for several sets of operating conditions.

FIG. 10 shows a vertical cross-section of the lower part of a wound exchanger in operation, enabling a diphasic fluid to circulate downwards in the exchanger.

FIG. 11 shows a vertical cross-section of the upper part of this same exchanger, incorporating a distribution device.

FIG. 12 shows a perspective view of part of the distribution device illustrated in FIG. 11.

FIG. 13 shows a diagrammatic cross-section of part of another downward distribution device.

The wound exchanger represented in FIGS. 1 to 4 enables heat to be exchanged between a homogeneous diphasic fluid circulating upwards inside the shell and two other fluids circulating downwards in two separate nests of tubes. It incorporates a device for distributing the diphasic fluid in accordance with the invention.

This exchanger consists of a cylindrical shell 1 and a cylindrical core 2 placed concentrically inside the shell 1. Two headers 3 and 4, each with a tubular plate 5 and 6, are placed at the two ends of the exchanger. A first nest of tubes 7, only one tube of which has been shown in FIGS. 1 and 2, in order to make the drawing clearer, is wound spirally around the core 2. The upper end of each tube 7 passes hermetically through the tubular plate 5, and the lower end through the tubular plate 6. Two spheres 8 and 9, which fulfill the function of headers, are placed at the two ends of the core 2, their centers being on the same axis as the shell 1 or core 2. The second nest of tubes 10, only one pipe of which has been shown in FIGS. 1 and 2, is wound spirally around the core 2. The nests of tubes 7 and 10 are combined around the core 2. The upper end of each tube 10 is connected to the sphere 8, and the lower end to the sphere 9. The wound exchanger is made airtight by means of two roughly cylindrical coverings 11 and 12, the diameter of which is greater than that of the shell 1. The covering 11, situated at the upper end of the exchanger, is connected hermetically to sphere 8, and the header 3. The covering 12, situated at the lower end of the exchanger, is similarly connected hermetically to the sphere 9 and the header 4. Two pipes 13 and I4, situated at the lower and upper ends of the exchanger respectively, supply and discharge the diphasic fluid. The pipes 15 and 16 supply and discharge respectively the fluid circulating in the first nest of tubes 7 wound around the core 2. The pipes 17 and 18 supply and discharge respectively the fluid circulating in the second nest of tubes 10.

The wound exchanger illustrated in FIGS. 1 and 2 need not be described in any greater detail. Only the lower part of the exchanger incorporating a device for distributing the diphasic fluid according to the invention is described below, with reference to FIGS. 1, 3 and 4.

The device for distributing the diphasic fluid is disposed in the shell 1. It comprises an annular horizontal distribution plate 19, disposed around the core 2 and dividing the shell 1, extended by the lower cylindrical cover 12, into an upstream or lower part and a downstream or upper part. The downstream part contains the winding of the exchanger. The upstream part incorporates a separator comprised by the inside of the cover 12.

A large number of upward pipes 20, with straight hexagonal cross-sections, only two of which have been shown in FIG. 3, pass through the plate 19. Their lower or upstream ends 124 and their upper or downstream ends 24 form two horizontal planes. The upper horizontal plane is situated slightly above the plate 19, and the lower horizontal plane below the interface between the liquid 21 and the gas 22 in the separator 12.

Two opposite sides of each hexagonal upward pipe 20 have a large number of vertically elongated perforations 23 these perforations are distributed vertically along each upward pipe 20 from its lower end and as far as the intersection with a third horizontal plane between the interface 21-22 and the plate 19. Each pipe is closed at its downstream end 24 and contains two cylindrical holes 25 opposite each other near the end 24.

In accordance with FIGS. 3 and 4, the distribution plate 19 is built up step by step around the core 2 by means of concentric crowns 26 of increasing diameter, disposed side by side and fitting together. These crowns rest on radial brackets 27, fixed rigidly to the core 2. Each pipe 20 passes through two coaxial hexagonal holes drilled through the upper wing 28 and lower wing 29 respectively of each crown 26. The pipes 20 are thus held and attached in the high position inside the separator 12. Each tube 7 or 10 in the first or second nest of tubes fits into and is held in place in notches 30 and 31 provided for the purpose in the upper wing 28 and lower wing 29 respectively.

Communication between the separator 12 and shell 1 is provided partly by the various clearances in the plate 19, resulting from assembly the clearance between the core 2 and the first crown, the clearance between the crowns 26, clearance between the last crown and the shell 1, the clearance in the notches 31 for tubes 7 and 10 of the winding and in the holes for the upward pipes 20. Additional communication is provided by the holes or channels 32 and 33, drilled through each lower wing 29 and upper wing 28 respectively, with all the lower wings 29 and upper wings 28 forming two perforated partitions close to each other.

The upward pipes 20 and tubes 7 and 10 may possibly be held in the lower position by means of lower stop crowns. Two concentric crowns 34 hold a single row of upward pipes 20 and tubes 7 and 10. These two crowns are fixed together by rivets (not shown) through the pipes 20. These crowns 34 together provide little resistance to the flow of any fluid moving vertically from the interior of cover 12 to the interior of shell 1.

The upward pipes 20 are not placed in just any way in their positions, determined by the coaxial hexagonal holes drilled through the upper wings 28 and lower wings 29 in each crown 26. The axis defined by the centers of the circular holes 25 opposite each other in each pipe 20 forms a constant angle to the radius perpendicular to the axis of the core and passing through the center of one of the said hexagonal holes. For the upward pipes 20 situated in a given zone of the plate 19, any fluid passing through them is thus distributed outside each pipe 20 in a roughly horizontal average direction, and all these directions are on one horizontal plane and are roughly parallel to one another.

When the installation is operating, the diphasic fluid arrives through the pipe 13 and reaches the separator inside the cover 12, usually in a very heterogeneous form. This fluid is separated into a liquid phase 21 and a gas phase 22, with an interface situated in the areas of perforations 23 of the upward pipes 20. Some of the perforations 23 are thus submerged by the liquid 21.

Since the separator inside cover 12 is under pressure in relation to the rest of the wound exchanger, part of the gas phase 22 moves into the upward pipes 20, through the perforations 23 left uncovered by the liquid 21. Each gas jet moves upwards in each upward pipe 20, mixing with a liquid jet representing a fraction of the liquid 21. A diphasic fluid is discharged from each pipe 20, through the holes 25, in a roughly horizontal average direction. The liquid 21 drawn along is distributed uniformly over the plate 19 and/or penetrates directly into the nest of tubes, homogeneously mixed with gas.

Another part of the gas phase 22 is injected through the perforations 32 and 33 in the plate 19 into the liquid surmounting it. By means of this passage into the liquid, a homogeneously distributed gas-liquid mixture is obtained upstream of the winding and downstream of the plate. This homogeneous diphasic fluid next circulates upwards in the shell 1 and around the tubes 7 and 10, exchanging its heat with the separate fluids circulat ing in the tubes 7 and 10 respectively.

The upward distribution device described above with reference to FIGS. 2, 3 and d forms one form of embodiment of the present invention. Other variants may also be used.

Different forms of upward pipes have been constructed, in accordance with FIGS. 5a5d. In accordance with FIG. 50, there is no side opening, hole or slit in the lower part of the upward pipes, and they extend upward from a horizontal plane above and close to the gas-liquid interface in the separator inside cover I2.

According to FIG. 5b, the upward pipes 20 also have a horizontal mouth-piece 35.

According to FIG. 50, the upward pipes have a hexagonal cross-section, and contain two vertical slits 36, extending from their lower end.

According to FIG. 5d, the pipes are cylindrical, and also contain two vertical slits 37. Different embodiments of these pipes are used, depending on the number of slits (one slit, two slits opposite each other, four slits set at to one another), or their thickness.

In another embodiment of the invention, the upward pipes 20 are of different lengths, giving the upward distribution device greater operating flexibility. Accord ing to FIG. 6, upward pipes 20, identical with those described earlier, of different lengths, are placed vertically, passing through the plate 19. Their upper ends are on a horizontal plane P,,, and their lower ends on three horizontal planes P,, P, and P By suitable distribution of these different pipes, it is possible to obtain improved flexibility, particularly during starting and stopping of an installation in which is included a wound exchanger of the type described above.

In another form of embodiment of the invention, the distribution plate 19 contains no perforations 32 or 33, and is thus more or less gastight. According to FIG. 7, the upward pipes 20 have lower portions identical to those of the upward pipes described earlier, while the upper portions are open, without any discharge opening 25. During operation the liquid can accumulate on the plate 19 up to a level corresponding to the horizontal plane on which .the upper ends of the pipes 20 lie. It is then drawn along and is added to the gas-liquid mixture discharged vertically by the upward pipes 20, to form a homogeneous diphasic fluid moving upwards.

As an example, a wound exchanger according to FIGS. 1 to 4, with an exchange surface of 4,l60 sq.m, has an overall length of l2.l m and the inside diameter of the cylindrical shell is 2.78 m. It incorporates a distribution device with the following characteristics inside diameter of the cover 12 3.2 m

height between the gas-liquid interface 21-22 and the plate 19 1 45 cm outside diameter of the core 57 cm total number of tubes 7 and 10 2,3l0

total number of upward pipes 20 4,620

The upward pipes have the following characteristics hexagonal section 14-16 mm between flat sections length 70 cm height of perforated areas 18.5 cm

width of slit 1 mm.

The plate 19 has the following characteristics area allowing fluid passage (because of various clearances) 260.5 sq.cm for all the upper wings 29 and 39.5 sq.cm between the last crown and the shell 1 perforated area for each upper partition 28 or lower partition 29 1,580 sq.cm.

The exchanger with these characteristics is combined with a natural gas liquefaction installation. In this case, the natural gas is cooled and liquefied by passing downwards through the nest of tubes 10, and a condensed cycle gas is cooled by passing downwards through the nest of tubes 7, and then injected after expansion into the separator 12 of the wound exchanger through the pipe 13. The gas-liquid mixture injected into the exchanger described above at the rate of 324,000 kg an hour includes 29.4 percent weight of vapor, while the liquid and gas have respective densities of the liquid and gas of 598 kg/cu.m and 3.02 kg/cu.m. When operating at 100 percent, 71 liters/min of gas and 1.38 liters/min of liquid pass through each upward pipe 20. The height of perforated area in contact with the gas phase 22 is 59 mm, and the pressure loss in each upward pipe 20 or the distribution device is 190 mm of water. All the perforations 23 in the upward pipes 20 are submerged when operating at between and 50 percent.

The operation of upward distribution devices according to the invention can be described by two series of curves.

According to FIG. 8, curves can be drawn for each upward pipe, giving the flow of liquid Q conveyed by each upward pipe in relation to the height of slit H not submerged by the liquid for pressure losses AP,, AP AP AP of increasing size and for a given operating pressure.

According to FIG. 9, curves can be drawn on the same graph to show the gas flow q, passing through each upward pipe in relation to the pressure loss Ah per upward pipe 20 and the gas flow Q,, passing through the perforated plate 19 in relation to the pressure loss AH in the said plate, for increasing percentages 0,, a a a, of the nominal flow of gas and liquid reaching the separator.

Mention will now be made of the different 'advantages offered by an upward distribution device according to the invention, with reference to FIGS. 8 and 9.

According to the right-hand part of the curve in FIG. 8, corresponding for instance to a pressure loss AP,, the flow ofliquid varies little in relation to the height of slit. This allows for slight manufacturing tolerances of the height of the slits, and provides greater manufacturing flexibility. For example, if the separated and homogeneously distributed gas-liquid mixture is a mixture of 50 percent ethane and 50 percent propane by volume, in thermodynamic equilibrium at five absolute atmospheres, for a pressure loss of 150 mm water, the liquid flow varies only by 6 percent if the tolerance of the height of the slits is mm. The usual tolerances are around 3 mm, so that one can be sure that all the upward pipes are discharging the same amount of liquid, and unifrom distribution of the liquid over the perforated plate is thus obtained.

According to the right-hand part of the curves AP,, AP;, AP AP any reduction in the height of slit free in an upward pipe corresponds to an increase in the liquid flow passing through the upward pipe. Any rise in the level of liquid in the separator is thus immediately compensated for by an increase in the flow of liquid passing through the upward pipes. The device is thus selfregulating, so long as the operating point is in the righthand part of the curves AP AP,, AP etc.

According to FIG. 9, there can be drawn on a single graph, the curves representing respectively the gaseous flowrate (curves in broken lines) passing into each riser tube, as a function of the loss of pressure Ah per riser tube 20, and the gaseous flow-rate Q, (curves in full lines) passing into the perforated plate 19, as a function of the loss of pressure AH in the said plate, for increas' ing percentages a,, a a;, of the nominal flow-rate of the two-phase fluid passing into the separator. The operating point of the device is defined by the intersection of the curves q, =f(Ah) and Q,,=f(AH) for a given percentage flow. Such intersections exist, for instance, at A, B and C. For an operating point between C and B, the operation is uneven, while it is stable at A.

In the case of a gas-liquid mixture in which the specific masses of gas and liquid are 8.24 kg/cu.m and 597 kg/cu.m respectively, point A corresponds to operation of the plant at percent mominal capacity, and point C to operation at 34 percent nominal capacity.

On the basis of this example, operation of the distribution device can be relied on in a very wide range of operating conditions for the installation, and is thus extremely flexible.

The wound exchanger according to FIGS. 10 to 12 allows an exchange of heat between a homogeneous diphasic fluid circulating inside the shell side in a downward direction, and two other fluids circulating upwards, in two different nests of tubes. It incorporates a device for distributing the diphasic fluid according to the invention.

The exchanger according to FIGS. 10 and 11 is similar in structure to the exchanger according to FIGS. 1 and 2. It need not be described in an greater detail here, therefore, and the same numerical references as for FIGS. 1 and 2 have been used in FIGS. 10 and 11.

In connection with FIGS. 11 and 12, only the upper part of the exchanger is described it incorporates a device for distributing the diphasic fluid according to the invention.

The device for distributing the diphasic fluid is disposed in the shell I. It includes an annular horizontal distribution plate 40, disposed around the core 2 and dividing the shell 1, extended by the upper cylindrical cover 12, into an upstream or upper part and a downstream or lower part. The downstream part contains the exchanger winding and the upstream part incorporates a separator comprised by the inside of the cover 12.

The separator comprises a first deflector 38 facing the pipe 13 this is basically a cylindrical wall extending laterally over an angle of about 30 to the center. The separator also comprises a second deflector 39, staggered in relation to the deflector 38.

Numerous pipes 41 and 42, with a straight hexagonal section, a few of which are shown in FIG. 11, pass through the plate 40. Their upper ends 43 and lower ends 44 each lie on a horizontal plane. The upper horizontal plane is situated slightly above the plate 40, and the lower one below, and very close to the plate 40.

The downward pipes 41 are more numerous than the pipes 42, the function of which will be described below. Each hexagonal downward pipe 41 has a short vertical slit 45 at the upper end 43 and extending downwards from the said upper end.

The lower ends of the slits 45 lie on a roughly horizontal plane. The pipes 41 are open at both ends. The pipes 42, hexagonal in section, are open at their upper end 43 and more or less closed at their lower end 44. Four sides of each pipe 42 have perforations 46, inside the plate 40, as described below.

The plate 40 is formed step by step around the core 2, from concentric crowns 47 of increasing diameter, disposed side by side and fitted together. FIG. 12 shows one of these crowns 47, similar to the crowns 26 described above, and through which pass the pipes 41 and 42, as well as tubes 7 and of the winding. These crowns are joined together by means of rivets through the hexagonal pipes 41 and 42. The upper wings 48 and lower wings 49 contain the holes needed for the passage of the pipes 41 and 42, and the notches 30 and 31 required for the passage of the tubes 7 or 10. The perforations 46 in the tubes 42 lie between the upper wings 48 and the lower wings 49.

Communication between the separator 12 and the duct 1 is partly provided, as above, by the various clear ances resulting from the construction of the plate 40. Additional communication is provided by holes 50 distributed uniformly and drilled through each upper wing 48 and each lower wing 49. All the upper wings together and all the lower wings together form two perforated partitions close to each other.

During operation, the diphasic fluid reaches the separator in the cover 12 through pipe 13, usually in the form of an extremely heterogeneous mixture. This fluid comes up against the deflector 38 and is separated into a liquid phase 21 and a gas phase 22, forming an interface above the plate 40 but below the slits in the pipes 41.

Since the separator in cover 12 is under pressure in relation to the rest of the wound exchanger, a large amount of the gas phase is drawn into the downward pipes 41.

The pressure is balanced on both sides of the upper wings 48 by means of the perforations 46 in the pipes 42, and so the liquid flows by gravity onto the lower wing 49, mainly through the perforations 50. Most of the pressure loss is carried over to the lower wings 49, so that the liquid is distributed uniformly over the upper wings 48, and during operation the liquid level is ascertained on the plate 40. in the event of an overflow, the liquid can be distributed uniformly and gradually through the slits 45 in the downward pipes 41. On the other hand, the liquid flows through the perforations in the lower wings 49 with a large pressure loss. A liquid seal can therefore be obtained or not on the lower perforated partition 49. In the event of the partition 49 being dry, this no longer affects the obtaining of a homogeneous diphasic fluid, since the uniform distribution of the liquid has been able to take place on the upper perforated partition 48.

The homogeneous diphasic fluid circulates downwards in the shell 1, around the pipes 7 and 10, ex-

changing its heat with the separate fluids circulating in the nests of tubes 7 and 10 respectively.

As an example, a wound exchanger with an exchange surface area of 800 sq.m has an overall length of 6.5 m, and the cylindrical shell has an inside diameter of 2.07 m. At the upper end it contains a device with the following characteristics outside diameter of the cover 12 2.3 m

outside diameter of the core 66 cm total number of pipes 7 and 10 800 total number of downward pipes 41 3,200

total number of balancing pipes 44 800.

The downward pipes 41 have the following characteristics hexagonal cross-section 14'16 mm between flat sections length 31 cm width of slits 45 1 mm height of slits 4S 20 mm lower opening in the pipes 41 1 cm from the lower wing 49.

The balancing pipes each have eight holes, 6 mm in diameter.

The plate 40 has the following characteristics area allowing liquid through 87.3 sq. cm

perforated area per lower or upper partition 153 sq.

The exchanger with these characteristics is combined with a natural gas liquifaction installation. in this case the natural gas is cooled and liquified by passing upwards in the nest of tubes 10 a condensed cycle gas is cooled by passing upwards in the nest of tubes 7, and then injected after expansion into the separator 12 of the wound exchanger, through the pipe 13. The gasliquid mixture, injected into the exchanger described above, at -143 C and 102 bars, at the rate of 100,000 kg an hour, contains 45.1 percent weight of liquid, the liquid and gas having respective densities of 547 kg/cu.m and 3.72 kg/cu.m. When operating at 100 percent capacity, 25 liters/min of gas pass through each downward pipe 41, and 41 liters/min through each balancing pipe 42. The level of liquid settles at 9 cm above the plate 40.

The lower perforated partition 49 is dry. The distribution device has an overall pressure loss of mm of water.

The downward distribution device according to FIGS. 11 and 12 may be modified according to the invention, as shown in FIG. 13.

According to FIG. 13, the plate 40 does not contain any perforation 50 or any balancing pipe 42. The downward pipes 41 contain lateral holes 51, a little above the plate 40.

During operation, the diphasic fluid is separated above the plate 40 into a liquid phase 21 and gas phase 22, forming an interface slightly above the holes 51 in the pipes 41. Part of the gas phase is drawn into the downward pipes 41, through the end 43. Each gas jet, moving downwards in each downward pipe 41 draws along and mixes with a liquid jet, penetrating into the pipe 41 through the hole or holes 51. The fluid jets thus obtained are discharged from the downward pipes 41 at their end 44, in a roughly vertical direction. A homogeneous diphasic fluid is obtained at the outlet from the downward distribution device according to P10. 13.

What is claimed is:

l. A heat exchanger of large cross section, for countercurrent heat exchange between a diphasic fluid and at least one other fluid, comprising a housing comprising a shell and closure members disposed one at each end of said shell; means defining a plurality of flofw paths for said other fluid inside said housing in fluid communication at one end with a distributor and at the other end with collector for said other fluid; a plate connected to said housing, substantially perpendicular to said shell, dividing said housing into a separation chamber for said diphasic fluid between a said closure member and said plate, and a heat-exchange chamber between said shell and plate and the other said closure member and enclosing the bulk of said plurality of flow paths; a first conduit for introducing said diphasic fluid into said separation chamber; means for separation of said diphasic fluid into a body of liquid phase and a body of gas phase above said body of liquid phase in said separation chamber; a plurality of distribution tubes, substantially parallel to said shell, distributed in a substantially unfform manner through the cross section of said plate, having an upstream portion extending from said plate into said separation chamber and a downstream portion extending into and terminating in said heat-exchange chamber between said plate and said bulk of the plurality of flow paths, each upstream portion of said distribution tubes being in fluid communication both with said body of liquid phase and with said body of gas phase in said separation chamber, each said downstream portion of said distribution tubes being in fluid communication with the whole of said heat exchange chamber thereby to discharge into said heat exchange chamber substantially homogeneous diphasic fluid on the shell side of said flow path defining means; and a second conduit for evacuating said fluid from said heat-exchange chamber after heat exchange with said another fluid.

2. A heat exchanger according to claim 1, wherein the upstream ends of the upstream portions of said plurality of distribution tubes are disposed in at least one transverse plane substantially parallel to said plate.

3. A heat exchanger according to claim 2, wherein the upstream ends of said plurality of distribution tubes define a plurality of spaced parallel transverse planes in which the said tubes are distributed in a substantially uniform manner.

4. A substantially vertical heat exchanger according to claim 1, for countercurrent heat exchange between said diphasic fluid flowing in an upward direction and said at least one other fluid flowing in a downward direction, said heat-exchange chamber being disposed above said separation chamber, wherein each upstream portion of each distribution tube comprises passage means extending along said portion from the lower end thereof for passing at least said part of the gas phase from said body of gas inside each tube, and each said upstream portion opens into said separation chamber at said lower end for introducing at least substantially equal portions of the liquid phase from said body of liquid phase into the gas phase flowing through each said distribution tube, thereby to produce a plurality of homogeneous fluid jets of the diphasic fluid corresponding respectively to said plurality of tubes, and thereby to pass and distribute the liquid phase into said part of the gas phase in a substantially uniform manner over the whole cross section of said exchanger above said plate.

5. A heat exchanger according to claim 4, wherein said passage means in said plurality of distribution tubes comprises a plurality of perforations the vertical extent of which is greater than the horizontal extent thereof.

6. A heat exchanger according to claim 4, wherein said passage means in said plurality of distribution tubes comprises twolengthwise slits situation in an axial plane of said tubes.

7. A heat exchanger according to claim 4, wherein the upstream ends of the upstream portions of said plurality of distribution tubes are disposed in at least one transverse plane substantially parallel to said plate, said passage means extending along each upstream portion of each distribution tube from said transverse plane to a second transverse plane substantially parallel to said plate.

8. A heat exchanger according to claim 4, wherein said plate comprises a plurality of passage means between said separation chamber and said heat-exchange chamber, distributed in a substantially uniform manner through the cross section of said plate, for passing and distributing another part of the gas phase in a substantially uniform manner over the cross section of said exchanger, downstream of said plate, into a portion of the liquid phase which has passed downstream of said plate and is evenly distributed and retained on said plate, thereby to produce another part of the homogeneous flow of the diphasic fluid.

9. A heat exchanger according to claim 8, wherein each downstream portion of each distribution tube is substantially closed at its upper end and comprises at least a port for passing the corresponding fluid jet from the inside of each said tube into the heat-exchange chamber in a mean substantially horizontal direction.

10. A heat exchanger according to claim 9, wherein the distribution tubes extend through said plate in such a manner that for a series of adjacent distribution tubes, the corresponding fluid jets pass into said heatexchange chamber in means directions substantially parallel to one another.

I l. A substantially vertical heat exchanger according to claim 1, for countercurrent heat exchange between a diphasic fluid flowing in a downward direction and at least one other fluid flowing in an upward direction, said separation chamber being disposed above said heat-exchange chamber, wherein each upstream portion of each distribution tube opens into said separation chamber at its upper end and each downstream portion of each said distribution tube opens into said heatexchange chamber at its lower end, for passing said gas phase from said body of gas inside each tube, and said plate comprises a plurality of passage means distributed in a substantially uniform manner through the cross section of said plate, for passing and distributing the liquid phase from said body of liquid phase into said gas phase in a substantially uniform manner over the whole cross section of said exchanger below said plate.

12. A substantially vertical heat exchanger according to claim 1, for countercurrent heat exchange between a diphasic fluid flowing in a downward direction and at least one other fluid flowing in an upward direction, said separation chamber being disposed above said heat-exchange chamber, wherein each upstream portion of each distribution tube opens into said separation chamber at its upper end and each downstream portion of each said distribution tube opens into said heatexchange chamber at its lower end for passing said gas phase from said body of gas inside each said tube, and each upstream portion of each distribution tube comprises passage means for introducing substantially equal portions of the liquid phase from said body of liquid phase into the gas phase flowing through each said distribution tube, thereby to produce a plurality of homogeneous fluid jets of the diphasic fluid corresponding respectively to said plurality of tubes, and thereby to pass and distribute the liquid phase into the gas phase in a substantially uniform manner over the corss section of said exchanger below said plate.

13. A heat exchanger according to claim 12 wherein the passage means of each distribution tube are located in the vicinity of said plate.

14. A heat exchanger according to claim 1 1, wherein ftO said plate comprises an upper partition and a lower partition substantially parallel to each other, both partitions having a plurality of passage means distributed in a substantially uniform manner through the cross section of said plate, defining therebetween an intermediate chamber, and wherein said plate comprises a plurality of pressure-balance tubes, substantially parallel to said shell, distributed in a substantially uniform manner through the cross section of said plate, having an upper portion extending from the upper partition into said separation chamber and opening thereinto, and a lower portion extending from said upper partition into said intermediate chamber and opening thereinto, for providing fluid communication of said intermediate chamber exclusively with said body of gas phase. 

1. A heat exchanger of large cross section, for countercurrent heat exchange between a diphasic fluid and at least one other fluid, comprising a housing comprising a shell and closure members disposed one at each end of said shell; means defining a plurality of flow paths for said other fluid inside said housing in fluid communication at one end with a distributor and at the other end with collector for said other fluid; a plate connected to said housing, substantially perpendicular to said shell, dividing said housing into a separation chamber for said diphasic fluid between a said closure member and said plate, and a heatexchange chamber between said shell and plate and the other said closure member and enclosing the bulk of said plurality of flow paths; a first conduit for introducing said diphasic fluid into said separation chamber; means for separation of said diphasic fluid into a body of liquid phase and a body of gas phase above said body of liquid phase in said separation chamber; a plurality of distribution tubes, substantially parallel to said shell, distributed in a substantially unfform manner through the cross section of said plate, having an upstream portion extending from said plate into said separation chamber and a downstream portion extending into and terminating in said heat-exchange chamber between said plate and said bulk of the plurality of flow paths, each upstream portion of said distribution tubes being in fluid communication both with said body of liquid phase and with said body of gas phase in said separation chamber, each said downstream portion of said distribution tubes being in fluid communication with the whole of said heat exchange chamber thereby to discharge into said heat exchange chamber substantially homogeneous diphasic fluid on the shell side of said flow path defining means; and a second conduit for evacuating said fluid from said heat-exchange chamber after heat exchange with said another fluid.
 2. A heat exchanger according to claim 1, wherein the upstream ends of the upstream portions of said plurality of distribution tubes are disposed in at least one transverse plane substantially parallel to said plate.
 3. A heat exchanger according to claim 2, wherein the upstream ends of said plurality of distribution tubes define a plurality of spaced parallel transverse planes in which the said tubes are distributed in a substantially uniform manner.
 4. A substantially vertical heat exchanger according to claim 1, for countercurrent heat exchange between said diphasic fluid flowing in an upward direction and said at least one other fluid flowing in a downward direction, said heat-exchange chamber being disposed above said separation chamber, wherein each upstream portion of each distribution tube comprises passage means extending along said portion from the lower end thereof for passing at least said part of the gas phase from said body of gas inside each tube, and each said upstream portion opens into said separation chamber at said lower end for introducing at least substantially equal portions of the liquid phase from said body of liquid phase into the gas phase flowing through each said distribution tube, thereby to produce a plurality of homogeneous fluid jets of the diphasic fluid corresponding respectively to said plurality of tubes, and thereby to pass and distribute the liquid phase into said part of the gas phase in a substantially uniform manner over the whole cross section of said exchanger above said plate.
 5. A heat exchanger according to claim 4, wherein said passage means in said plurality of distribution tubes comprises a plurality of perforations the vertical extent of which is greater than the horizontal extent thereof.
 6. A heat exchanger according to claim 4, wherein said passage means in said plurality of distribution tubes comprises two lengthwise slits situation in an axial plane of said tubes.
 7. A heat exchanger according to claim 4, wherein the upstream ends of the upstream portions of said plurality of distribution tubes are disposed in at least one transverse plane substantially parallel to said plate, said passage means extending along each upstream portion of each distribution tube from said transverse plane to a second transverse plane substantially parallel to said plate.
 8. A heat exchanger according to claim 4, wherein said plate comprises a plurality of passage means between said separation chamber and said heat-exchange chamber, distributed in a substantially uniform manner through the cross section of said plate, for passing and distributing another part of the gas phase in a substantially uniform manner over the cross section of said exchanger, downstream of said plate, into a portion of the liquid phase which has passed downstream of said plate and is evenly distributed and retained on said plate, thereby to produce another part of the homogeneous flow of the diphasic fluid.
 9. A heat exchanger according to claim 8, wherein each downstream portion of each distribution tube is substantially closed at its upper end and comprises at least a port for passing the corresponding fluid jet from the inside of each said tube into the heat-exchange chamber in a mean substantially horizontal direction.
 10. A heat exchanger according to claim 9, wherein the distribution tubes extend through said plate in such a manner that for a series of adjacent distribution tubes, the corresponding fluid jets pass into said heat-exchange chamber in means directions substantially parallel to one another.
 11. A substantially vertical heat exchanger according to claim 1, for countercurrent heat exchange between a diphasic fluid flowing in a downward direction and at least one other fluid flowing in an upward direction, said separation chamber being disposed above said heat-exchange chamber, wherein each upstream portion of each distribution tube opens into said separation chamber at its upper end and each downstream portion of each said distribution tube opens into said heat-exchange chamber at its lower end, for passing said gas phase from said body of gas inside each tube, and said plate comprises a plurality of passage means distributed in a substantially uniform manner through the cross section of said plate, for passing and distributing the liquid phase from said body of liquid phase into said gas phase in a substantially uniform manner over the whole cross section of said exchanger below said plate.
 12. A substantially vertical heat exchanger according to claim 1, for countercurrent heat exchange between a diphasic fluid flowing in a downward direction and at least one other fluid flowing in an upward direction, said separation chamber being disposed above said heat-exchange chamber, wherein each upstream portion of each distribution tube opens into said separation chamber at its upper end and each downstream portion of each said distribution tube opens into said heat-exchange chamber at its lower end for passing said gas phase from said body of gas inside each said tube, and each upstream portion of each distribution tube comprises passage means for introducing substantially equal portions of the liquid phase from said body of liquid phase into the gas phase flowing through each said distribution tube, thereby to produce a plurality of homogeneous fluid jets of the diphasic fluid corresponding respectively to said plurality of tubes, and thereby to pass and distribute the liquid phase into the gas phase in a substantially uniform manner over the corss section of said exchanger below said plate.
 13. A heat exchanger according to claim 12 wherein the passage means of each distribution tube are located in the vicinity of said plate.
 14. A heat exchanger according to claim 11, wherein said plate comprises an upper partition and a lower partition substantIally parallel to each other, both partitions having a plurality of passage means distributed in a substantially uniform manner through the cross section of said plate, defining therebetween an intermediate chamber, and wherein said plate comprises a plurality of pressure-balance tubes, substantially parallel to said shell, distributed in a substantially uniform manner through the cross section of said plate, having an upper portion extending from the upper partition into said separation chamber and opening thereinto, and a lower portion extending from said upper partition into said intermediate chamber and opening thereinto, for providing fluid communication of said intermediate chamber exclusively with said body of gas phase. 